Rapid advances in electronics have resulted in production of electronic calculators having impressive computational capabilities. Arithmetically powerful calculators have proven their general utility, but are not well suited to certain computational needs of some groups of calculator users. In recognition of needs not met by general purpose calculators, many special purpose calculators (for example, a calculator designed to help shoppers select best shopping value, Marmon--U.S. Pat. No. 4,334,278) have been developed. The invention described herein is intended to meet the need of students, technicians, chemists, and others for a computational device that facilitates calculations in chemical stoichiometry.
The computational method most appropriate to chemical stoichiometry is called "dimensional analysis", comprising a sequence of multiplications by unit conversion factors such that, in stoichiometry, a number having a given chemical unit is converted to an equivalent number having a different chemical unit. A similar non-chemical problem, using numerically invariable conversion factors, would be calculating the number of nanometers equal to one mile: ##EQU1## Many calculators do perform similar unit conversions using a singal, invariable conversion factor. Such calculators cannot simplify computation in chemical stoichiometry as they are not designed to facilitate step-wise unit conversions using variable, user-input conversion factors. The electronic device described herein performs common arithmetic operations, and specifically utilizes chemical units input by the user to automatically effect stoichiometric conversions, thereby greatly facilitating computations for students and others.